Adenoviral vector systems for gene transfer into skeletal muscle have the advantages of relatively large cloning capacity, growth to high titre in vitro, and the ability to transduce non-dividing cell populations. Additional vector modifications outlined in unit 1 could extend the cloning capacity to accommodate a full-length dystrophin cDNA. A major issue to be addressed prior to clinical application of this technology is the need for an improved understanding of the biology of diffusion barriers to adenoviral delivery in vivo. The microvascular endothelium represents the major diffusion barrier to be overcome in the systemic delivery of adenovirus to skeletal muscle. We show preliminary data to support the hypothesi that changes in either capillary permeability or transcapillary pressure gradient can have a dramatic impact on the efficiency of adenovirus mediated gene transfer into skeletal muscle. We propose an experimental plan for the study of additional interventions that offer to further improve gene transfer to striated muscle and minimize unwanted delivery to sites of documented toxicity. We will systematically study the impact of high pressure perfusion and alteration in the contractile state of endothelial cells on the process of transendothelial diffusion of marker adenovirus. In the second half of the project we will explore the use of these interventions in conjunction with extracorporeal circulatory support (ECMO) to properly evaluate the maximal degree of transendothelial adenoviral diffusion attainable. The experiments described have two overall goals. In the near term, the principal goal is the development of adenoviral delivery schemes to aid ina the integration of the experimental plans of the other units, especially with regard to the physiologic assay of somatically delivered recombinant dystrophin in animal model systems. The primary long term goal is to develop a clinically applicable protocol for systemic adenovirus mediated gene transfer. This process will be specifically targeted towards patients with Duchenne Muscular Dystrophy. It is anticipated that successful delivery schemes will have additional applicability in the clinical management of other diseases states.